1. Technical Field
The invention is generally related to power amplifiers and, more particularly, is related to adjusting impedance of a power amplifier system.
2. Related Art
With the increasing power efficiency demands from users of mobile communication devices, such as cell phones and the like, mobile communication device manufacturers are continually searching for ways to improve power consumption efficiency within the mobile communication device, thereby increasing the useful operating period that a mobile communication device gets from a single charge of the power source, such as, but not limited to, a battery or fuel cell. During a normal voice conversation by a person using the mobile communication device, the transmitting function consumes a very large amount of available power. As such, energy conservation in transmitters is of paramount importance.
Conventional mobile communication devices typically consume large amounts of power as a voice signal is converted into a communication signal and amplified to a power level necessary for transmission from the mobile communication device to a base station. Within the communication industry, significant efforts continue to attempt to minimize power consumption. Therefore, there is an ongoing need to continue to reduce energy consumption in mobile communication devices.
The invention provides for adjusting impedance of a power amplifier system. One embodiment is a method for adjusting impedance of a power amplifier system comprising combining an output of a first power amplifier with an output of a second power amplifier via a coupler that couples an output connection of the first power amplifier with an output connection of the second power amplifier, wherein a prematching impedance network coupled to the second power amplifier adjusts a system impedance to a first value when the second power amplifier is not actuated, and wherein the prematching impedance network adjusts the system impedance to a second value when the second power amplifier is actuated.
In another embodiment, a system that adjusts impedance of a power amplifier system comprises a first power amplifier amplifying a communication signal; a bias controller for outputting a control signal, the bias controller coupled to a node in a communication device such that the communication signal is sensed; a second power amplifier responsive to the control signal, such that the bias controller activates the second power amplifier when an amplitude of the communication signal is at least equal to a predetermined amplitude, and such that the bias controller deactivates the second power amplifier when the amplitude of the communication signal is less than the predetermined amplitude; and a prematching impedance network coupled to at least the second power amplifier such that when the bias controller activates the second power amplifier the prematching impedance network adjusts a system impedance to a first value when the first power amplifier is activated, and such that when the bias controller deactivates the second power amplifier the prematching impedance network adjusts the system impedance to a second value when the first power amplifier and the second power amplifier are activated.
Other systems, methods, features and advantages of the invention will be or will become apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the invention, and be protected by the accompanying claims.